reduce android app apk size

Author: dongyuwei

android/app/build.gradle

@@ -86,12 +86,12 @@ apply from: "../../node_modules/react-native/react.gradle"
  * Upload all the APKs to the Play Store and people will download
  * the correct one based on the CPU architecture of their device.
  */
-def enableSeparateBuildPerCPUArchitecture = false
+def enableSeparateBuildPerCPUArchitecture = true
 
 /**
  * Run Proguard to shrink the Java bytecode in release builds.
  */
-def enableProguardInReleaseBuilds = false
+def enableProguardInReleaseBuilds = true
 
 android {
     compileSdkVersion rootProject.ext.compileSdkVersion
@@ -129,6 +129,7 @@ android {
     buildTypes {
         release {
             minifyEnabled enableProguardInReleaseBuilds
+            shrinkResources true
             proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
             signingConfig signingConfigs.release
         }